1. Field of the Invention
This invention generally relates to methods and apparatus for bone resection to allow for the interconnection or attachment of various prosthetic devices with respect to the patient. More particularly, the present invention relates to methods and apparatus for minimally invasive arthroplasty that permits bone resection at a joint through smaller incisions and with less potential for soft tissue damage.
2. Background Art
Different methods and apparatus have been developed in the past to enable a surgeon to remove bony material to create specifically shaped surfaces in or on a bone for various reasons including to allow for attachment of various devices or objects to the bone. Keeping in mind that the ultimate goal of any surgical procedure is to restore the body to normal function, it is critical that the quality and orientation of the cut, as well as the quality of fixation, and the location and orientation of objects or devices attached to the bone, is sufficient to ensure proper healing of the body, as well as appropriate mechanical function of the musculoskeletal structure.
In total knee replacements, for example, a series of planar and/or curvilinear surfaces, or “resections,” are created to allow for the attachment of prosthetic or other devices to the femur, tibia and/or patella. In the case of the femur, it is common to use the central axis of the femur, the posterior and distal femoral condyles, and/or the anterior distal femoral cortex as guides to determine the location and orientation of distal femoral resections. The location and orientation of these resections are critical in that they dictate the final location and orientation of the distal femoral implant. It is commonly thought that the location and orientation of the distal femoral implant are critical factors in the success or failure of the artificial knee joint.
Even though the trend in many surgical procedures has been to adopt techniques that are minimally invasive so as to reduce both the size of the incision and the amount of damage to soft tissue surrounding the joint, the need for precision in the location and orientation of resected bone cuts for arthroplasty procedures has limited the use of existing minimally invasive surgical techniques. Conventionally, femoral and tibial resections in total knee arthroplasty have been performed primarily through an incision made across the anterior (front) of the knee joint. U.S. Pat. No. 5,810,827 shows a technique for arthroplasty that involves making the resection cuts via incisions on either the medial or lateral sides. A similar approach to minimally invasive techniques for knee arthroplasty is described in U.S. Patent Publ. Appls. 2003/0100906A1, 2003/0171757A1 and 2003/0212413A1. While a medial or lateral approach has the potential to reduce soft tissue damage as compared to the anterior approach of conventional arthroplasty techniques, the size of the incision is still dictated by the size of the cutting tools and the size of the prosthetic implants.
Efforts have been made to reduce the effective size of prosthetic implants, either by making the prosthetic implant smaller or by making the prosthetic implant modular. The unicondular or “uni” implant for knee replacements, for example, is designed to replace just one of the two condyles on the femur and therefore is smaller than the implant prosthesis required for a total knee arthroplasty (TKA). Modular implants, where the implant is comprised of multiple interlocking components, have been used for both knee and hip replacements as another approach to making the size of the prosthetic implant smaller.
Although the effective size of prosthetic implants is being made smaller, it would be desirable to provide instrumentation and cutting tools that also reduced the requirements for incision size and minimized soft tissue damage, while still being able to provide the necessary precision and location to create the resected surfaces for such implants.